This invention relates to a lubricating system for a two cycle engine and more particularly to an improved system for lubricating a two cycle engine without creating excessive exhaust smoke.
The advantages of two cycle engines due to their simplicity and relatively high power output for displacement are well known. One of the advantages of a two cycle engine is that it does not normally employ a recirculating lubricating system of the type employed with four cycle engines One way in which two cycle engines have frequently been lubricated is by the mixing of lubricant with the fuel burned by the engine. However, this is not always advantageous even though it has the advantage of simplicity. The reason for this is that the amount of lubricant required may not be directly related to the amount of fuel consumed. In addition, there may be difficulties with insuring that all components of the engine receive adequate lubrication when lubricant is only mixed with the fuel.
There have, therefore, been proposed lubricant systems for two cycle engines wherein lubricant is supplied to at least some of the components of the engine directly from a lubricant tank for lubrication. With these systems, the lubricant delivered to the engine is normally drained into the crankcase and then will pass into the combustion chamber with the intake charge and be burnt and exhausted with the exhaust gases. If lubricant accumulates to an excessive level in the crankcase, this may give rise to an objectionable condition of providing exhaust smoke. Furthermore, the emission of excess lubricant through the exhaust system can give rise to certain pollution problems
Although the problem of exhaust smoke and exhaust pollution can be controlled by reducing the amount of lubricant delivered to the engine, this can provide some problems in the event that the amount of lubricant supplied is not adequate for all components.
It is, therefore, a principal object of this invention to provide an improved lubricating system for a two cycle engine wherein exhaust smoke and exhaust pollution is controlled.
It is a further object of this invention to provide an improved lubricating system for an internal combustion engine operating on the two cycle crankcase compression principle wherein adequate lubricant is supplied to all components of the engine but exhaust of lubricant in either burned or unburned form is effectively controlled.
One way in which exhaust smoke can be avoided is by providing a recirculating lubricating system for a two cycle engine. However, with such recirculating systems, it is necessary to insure that lubricant from withdrawn from the crankcase chambers and returned to the recirculating tank before any significant amount can accumulate. The reason for this is that the intake charge will flow through the crankcase and any lubricant which may have accumulated there will be swept into the combustion chamber even if a recirculating system is employed The problem is particularly acute in conjunction with the lubrication of the crankshaft and particularly its main bearing journals. This is one of the most highly stressed portions of the engine and it is essential to insure that it receives adequate lubrication. If a recirculating system is employed, then it is necessary to draw lubricant from each of the main bearing journals and return it to the separate recirculation tank. This provides a very complicated and expensive system.
It is, therefore, a further object of this invention to provide an improved lubricating system for a two cycle engine wherein a partial recirculating system is employed for lubricating parts of the engine including crankshaft journals that are easily accessible externally of the engine.